This invention relates in general to vehicle wheels and in particular to a two piece vehicle wheel having a partial wheel rim mechanically pinned to a fill face wheel disc and a process for fabricating such a wheel.
It is known in the art to fabricate a vehicle wheel by attaching a wheel rim to a separately formed wheel disc. Typically, the wheel rim is rolled from steel strip stock and the disc is stamped from steel sheet stock. The rim is welded to the disc to form the wheel. Such a wheel is shown in U.S. Pat. No. 5,257,455 to Iwatsuki. Alternately, the wheel rim can be rolled from steel and the wheel disc cast or forged from a light weight metal, such as aluminum, titanium or magnesium, or an alloy of a light weight metal. Because the metals forming the rim and disc are different, a ferrous weld anchor is usually attached to the wheel disc. The wheel rim is welded to the weld anchor to assure that a good weld is formed between the rim and the disc. Such a wheel is described in U.S. Pat. No. 3,506,311 to Nobach and is commonly referred to a bimetal wheel. A bimetal wheel combines the economy, flexibility and strength of a steel rim with the pleasing ornamental appearance of three dimensional contours formed in a cast or forged wheel disc. It also is known to form the wheel rim from an alloy of a light weight metal, in which case it might be possible to eliminate the weld anchor.
To enhance the appearance of a two piece wheel, it is known to attach a wheel disc which includes the outboard tire retaining flange to a partial wheel rim. Such a wheel is commonly referred to as a full face wheel. When a tire is mounted upon a full face wheel, the joint between the wheel disc and wheel rim is completely hidden and only the wheel disc is visible. A decorative finish is often applied to the face of the wheel disc to further enhance the appearance of the wheel. Examples of typical decorative finishes include metal plating, such as chromium plating, clear coatings and paint.
Referring now to the drawings, there is shown in FIG. 1, a fragmentary sectional view of a typical prior art bimetal full face wheel 10. The wheel 10 is described in the Nobach patent listed above and includes a full face wheel disc 11 formed from a light weight metal or light weight metal alloy by a conventional process, such as gravity or low pressure casting, or forging. The full face wheel disc 1 includes a central wheel hub (not shown) which is supported by a plurality of wheel spokes (one shown) within an annular sidewall 12. An outboard tire bead retaining flange 13 extends in an outward radial direction from the sidewall 12.
A ring-shaped weld anchor 15 formed from a ferrous material, such as steel, is partially embedded in the wheel disc sidewall 12. An exposed portion of the weld anchor 15 forms a welding surface 16. An alternate structure for the weld anchor is disclosed in U.S. Pat. No. 5,421,642 to Archibald where the weld anchor includes an annular collar which is received by the outboard end of a partial wheel rim. The weld anchor collar positions the wheel rim on the wheel disc. The wheel disc 11 shown in FIG. 1 further includes a cylindrical collar 17 which extends axially from the inboard side of the sidewall 12. The collar 17 also extends radially over a portion of the weld anchor 15 to secure the weld anchor 15 to the wheel disc 11.
A conventional partial wheel rim 20 is attached to the inboard side of the wheel disc 11. The wheel rim 20 is typically formed from steel strip stock with conventional rim roll forming machinery. The wheel rim 20 includes a cylindrically-shaped outboard end 22. The outboard wheel rim end 22 includes an outboard tire bead seat 23 and outboard safety bead 24. The outboard rim end 22 extends over the wheel disc collar 17 and into contact with the welding surface 16 of the weld anchor 15. Typically, the outboard rim end 22 and the wheel disc collar 17 are sized to form a clearance fit therebetween, allowing the wheel rim 20 to be rotated relative to the wheel disc 11.
A continuous circumferential air-tight weld 25 is formed between the wheel rim 20 and the weld anchor 15. Typically, a conventional friction or inertial welding process is used to form the weld 25. During the welding process, the wheel disc 11 is held stationary while the wheel rim 20 is rotated with the outboard rim end 22 pressed against the weld anchor 15. The friction between the rim end 22 and the weld anchor 15 generates sufficient heat to partially melt the outboard wheel rim end 22 and the adjacent portion of the weld anchor 15 to form the weld 25. Alternately, the wheel disc and rim assembly can be rotated while one or more welding torches form the weld 25.
Referring now to FIG. 2, there is shown a flow chart for a known manufacturing process for fabricating the full face wheel 10 illustrated in FIG. 1. In functional block 30 a full face wheel disc is formed by a conventional process, such as casting or forging. A weld anchor is embedded in the wheel disc during the casting or forging process. Alternately, a weld anchor can be secured to an inboard surface of the wheel disc after the wheel disc has been formed. The wheel disc is heat treated in functional block 31 and then machined to final shape in functional block 32.
While the wheel disc is being formed, a flat strip of metal is rolled into a circular hoop and the ends butt welded together in functional block 35. The hoop is shaped into a partial wheel rim in functional block 36 by a conventional process, such as rolling or spinning.
In functional block 37, the partial wheel rim is attached to the wheel disc formed in functional blocks 30 through 32 by a conventional welding process. The weld extends circumferentially around the wheel and forms an air-tight seal between the wheel rim and wheel disc. Typically, it is difficult to weld the hoop concentrically upon the disc. If the outboard and inboard tire bead seats of the assembled wheel are outside the required tolerance limits for concentricity, undesirable vibrations may occur when the wheel is mounted upon a vehicle and the vehicle operated. Accordingly, the tire bead seats of the assembled wheel are machined in functional block 38 to assure that the required amount of concentricity is achieved.